Yet Another Reason to Think Twice About Eating Meat

Earlier this year, the USDA found itself in hot water after an internal newsletter promoted “Meatless Mondays” in its cafeterias as part of a healthy eating initiative. The USDA eventually retracted their endorsement of the campaign after outcry from the livestock industry and farm state Congressmen, but the health benefits of eating less meat have long been established. Red meat consumption has been linked to increased risk of heart disease, diabetes and certain types of cancer. Now, a population-based study from researchers at the University of Chicago Medicine provides more evidence that it might be wise to take a break from steaks and pork chops every now and then.

Brisa Aschebrook-Kilfoy, PhD, research associate (assistant professor) in the Department of Health Studies, and Brian Chiu, PhD, associate professor of epidemiology, compared the eating habits of a group of patients newly diagnosed with non-Hodgkins lymphoma, a type of cancer of the immune system. They found that red meat consumption is associated with higher risk for the disease.

They surveyed the group on how much meat they ate, what types (beef, pork, chicken, etc) and how it was cooked, then linked this data to a database from the National Cancer Institute to calculate the amount of mutagens, or potential cancer-causing agents, consumed. They also cross-referenced a database maintained by the University of Minnesota to calculate the amount of nutrients in the meat.

Based on these calculations, they found evidence that different components of meat were linked to different subtypes of lymphoma, Diffuse large B cell lymphoma, the most common subtype, was associated with the amount of fat in the meat, whereas follicular lymphoma, the second-most common, was associated with levels of mutagens in the meat.

Aschebrook-Kilfoy said this evidence for a different mechanism between the two subtypes was one of their most interesting findings. “The epidemiologic patterns for the different subtypes are quite different, so people have thought that there were different causes. Looking at subtypes is a more informative way of doing research,” she said.

Chiu said that an epidemiological study like this should only be used as a guide for further research on the actual mechanisms that might be causing the cancer. But, he said, there are some possible explanations.

“We know a higher amount of animal fat will impair your immune function. When your immune function is suppressed that puts you at higher risk of developing lymphoma, because it’s a malignancy of the immune system,” he said. “A high amount of protein also induces chronic stimulations to the immune system. Once your immune system is chronically stimulated it makes you less responsive to challenges. That’s why some researchers think high protein also puts you at higher risk of lymphoma.”

He said carcinogens in the meat from the way it was cooked could also contribute to the higher risk of lymphoma, as could chemicals like pesticides that the animal may have ingested.

Nevertheless, Chiu said they’re not ready to make recommendations about the number of servings of meat you should eat, or how often. But given the evidence, he said it might be wise to follow an old rule of thumb.